It's weird that synthetic marijuana exists when regular pot is probably much easier to get.

But that isn't stopping teens — and it just sent 3 of them to the hospital with altered mental states and seriously elevated heart rates.

Here's what happened:

A 16-year-old girl was brought in by her boyfriend — and she refused to move or speak and did not respond when doctors rubbed her chest hard or pinched her! Her pulse was 105… and she was lying down.

She had smoked something called K2 which is a synthetic, and she had smoked marijuana as well. She (of course) tested positive for THC.

The synthetics were only recently banned in the U.S. and the Drug Enforcement Administration and there is a movement to classify them permanently as schedule 1 controlled substances. Like heroin.

So what are they exactly? They're blends of herbs and spices laced with cannabis-like chemicals… and they're believed to be much stronger than regular pot.

Here's what a doctor had to say:

"Because it's unregulated we don't know exactly what's in it. If people were getting the effects that they wanted they probably wouldn't be calling the poison control center. Anytime your teenager is acting abnormally or having aggressive agitation you should certainly seek medical attention."